The present invention relates to a roller bearing, and more particularly to a direction of a streaked grinding trail left on a roller end face at a time of grinding the roller end face.
A tapered roller bearing is structured such that a plurality of tapered rollers are interposed between an inner ring member and an outer ring member, a flange having a guide surface guiding end faces of the tapered rollers in a slide contact is provided in an end portion in an axial direction of the inner ring member, and they are lubricated by a lubricating agent such as an oil, a grease or the like. When grinding the end faces of the tapered rollers and the guide surface of the flange of the inner ring member, a streaked grinding trail is left thereon. A description will be given of the streaked grinding trail with reference to FIG. 16. A reference symbol 4A denotes an end face of a tapered roller, and a reference symbol 8 denotes a guide surface of a flange of an inner ring member. Streaked grinding trails lay of roughness T1 are left on the end surface 4A in a circumferential direction so as to form a number of concentric circles. Streaked grinding trails lay of roughness T2 in a circumferential direction are left on the guide surface 8 of the inner ring member 3.
When the streaked grinding trails lay of roughness T1 and T2 are left in the state mentioned above, it is hard for the end face 4A of the tapered roller to form a lubricating oil film due to a lack of lubricating oil content in a slide contact portion A between the end face 4A and the guide surface 8 of the inner ring member at a time of a high load or a high speed rotation. Further, there is a risk that a lack or a seizure of the lubricating oil film is generated.
Accordingly, a main object of the present invention is to provide a roller bearing which improves a seizure resisting property at a time of being rotated at a high load and a high speed.
The other objects, features and advantages of the present invention will be apparent from the following description.
In short, the present invention is as follows.
A roller bearing of the present invention includes an inner ring member, an outer ring member concentrically arranged in an outer side in a diametrical direction of the inner ring member, and a plurality of rollers provided between the inner ring member and the outer ring member so as to freely roll, wherein a flange having a guide surface guiding end faces of the rollers in a slide contact is provided in an end portion in an axial direction of at least one of the inner ring member and the outer ring member, and a number of microscopic streaked grinding trails lay of roughness are left on the end faces of the rollers in multiple directions.
In accordance with the roller bearing of the present invention, since a number of microscopic streaked grinding trails lay of roughness are left in multiple directions on the end faces which is in slide contact with the guide surfaces of the flanges in the rollers, a lubricating film is easily formed in the slide contact portion between the guide surfaces and the roller end faces, so that the lubricating oil film is hardly broken. Subsequently, since a metal contact is hardly generated in the slide contact portion, and a heat generation is restricted, a trouble such as a seizure or the like is restricted and a seizure resisting property is improved therewith.
The above-mentioned term xe2x80x9cmicroscopicxe2x80x9d means that a depth of unevenness of the streaked grinding trail is from a sub xcexcm to a xcexcm order. Further, the term xe2x80x98multiple directionsxe2x80x99 mentioned above includes two or more different directions which are different from a circumferential direction. Further, the mutual relation of directions may be provided with a regularity or not provided therewith. Further, the streaked grinding trail includes a recess groove striation, and an aspect of the striation includes a curve aspect, a linear aspect, the all other streaked aspects, or combined aspects thereof, and does not depend upon a change of the streaked width or aspect thereof.
The roller bearing in accordance with the present invention may have a number of microscopic streaked grinding trails lay of roughness left on the guiding surfaces of the flanges in multiple directions. In this case, since the streaked grinding trails lay of roughness of the guide surfaces are left in the multiple directions in the same manner, an oil film forming capacity becomes high, so that a problem such as the seizure or the like is restricted. In particular, since the tapered roller bearing provided with the flanges which makes a slide contact with the large diameter side end face flanges in the inner ring member is frequently used under a condition in which the flange guide surfaces and the roller end faces are in contact with each other due to a high load, it is extremely hard to form the lubricating oil film in this contact portion, and the problem such as the seizure or the like is easily generated. Accordingly, in the tapered roller bearing, it is preferable to form the streaked grinding trails lay of roughness on the large diameter side end faces of the tapered rollers or on the guide surfaces of the inner ring member being in slide contact with the roller large diameter side end faces in multiple directions. Since the streaked grinding trails lay of roughness on the large diameter side end faces of the tapered rollers are formed in the multiple directions, whereby the lubricating oil film is easily formed between the contact surfaces in the slide contact with the guide surfaces of the flanges, the structure is made such that the lubricating oil film is not broken or does not become thin between the contact surfaces. Accordingly, the structure is made such that it is possible to prevent the lubricating oil film from being broken and the problem such as the seizure or the like is not generated. Further, it is preferable the microscopic streaked grinding trails lay of roughness left on the roller end faces are left in multiple directions under a condition satisfying the following formula (1):
xcex3=L2/L1xe2x89xa62.5xe2x80x83xe2x80x83(1) 
in which, xcex3: surface pattern parameter of the roller end face, L1: a correlation length of roughness in a radial direction on the roller end face, and L2: a correlation length of roughness in a circumferential direction on the roller end face. The correlation length herein corresponds to a length until a auto-correlation coefficient becomes 0.5. The streaked grinding trails lay of roughness are structured such as to be provided with a multi-directivity defined quantitatively by the formula (1) mentioned above, whereby as is apparent from test results, it is possible to restrict a deviation of directions of the streaked grinding trails lay of roughness on the roller end faces at a time of grinding, it is possible to keep the oil film forming capacity high at a time when a lubricating environment in the roller end face is deteriorated, and it is possible to greatly improve a seizure resisting property of the roller bearing.